If it is reasonably certain that the woman is not pregnant, COCs can be initiated on any day of the menstrual cycle (additional contraceptive precautions are required if started after day 5).

If 1 active pill is missed, no additional precautions are needed.

If 2 active pills are missed (or a new pack is started 2 days late), additional precautions should be taken for 7 days.

A pill is regarded as missed if it is taken more than 24 hours late. In this event, the most recent missed pill should be taken as soon as possible (any earlier missed pills being omitted) and the rest of the pack as normal.

If 2 pills have been missed in the first week of a pack and the woman has had unprotected sex within the previous 7 days, emergency contraception may be needed.

If the pills have been missed in the third week of a pack, the 7-day break (or the 7 placebo pills, in the case of everyday preparations) should be omitted and the next pack started immediately.